1. Field of the Invention
This invention relates generally to photonic band gap technology.
2. Related Art
In recent years, advances in photonic technology have generated a trend toward the integration of electronic and photonic devices. These devices offer an array of advantages over conventional electronic devices. For example, they can provide enhanced speed of operation and reduced size. In addition, these devices are robust and provide resistance to environmental changes, such as rapid temperature variations, increased lifetime, and the ability to handle high repetition rates. These structures can be made of metals, semiconductor materials, ordinary dielectrics, or any combination of these materials.
In photonic band gap (PBG) structures, electromagnetic field propagation is forbidden for a range of frequencies, and allowed for others. The nearly complete absence of some frequencies in the transmitted spectrum is referred to as a photonic band gap PBG, in analogy to semiconductor band gaps. This phenomenon is based on the interference of light. For frequencies inside the band gap, forward-propagating and backward-propagating signal components can destructively cancel inside the structure, leading to nearly zero transmission and nearly complete reflection.
For example, recent advancements in PBG structures have been made in the development of a photonic band edge non-linear optical limiter and switch. See M. Scalora, et al., Optical Limiting and Switching of Ultrashort Pulses in Non-linear Photonic Band-Gap Materials, Phys. Rev. 73, 1368 (1994) (incorporated herein by reference in its entirety). Also, advancements in photonic technology have been achieved with the development of the non-linear optical diode. See M. Scalora et al., The Photonic Band-Edge Optical Diode, J App. Phys. 76, 2023 (1994) (incorporated by reference herein in its entirety). In addition, the physical processes involved in the photonic signal delay imparted by a uniform PBG structure are described in detail in Scalora et al., Ultrashort Pulse Propagation at The Photonic Band Edge: Large Tunable Group Delay with Minimal Distortion and Loss, Phys. Rev. E Rapid Comm. 54, 1078 (1996) (incorporated by reference herein in its entirety).
There is a need to control the transmissivity and reflectivity properties of a photonic band gap structure to thereby implement efficient, compact, and easily controlled photonic band gap devices, such as a non-linear optical switch or mirror, a non-linear gain medium, and a non-linear optical limiter.
The present invention provides a new method and device for controlling a non-linear reflectivity and non-linear transmissivity of a photonic pump signal incident on a photonic band gap (PBG) structure using a photonic control signal. The photonic pump and control signals can be continuous or pulsed, as required. Advantageously, the non-linear reflectivity and the non-linear transmissivity of the pump signal can be significantly and controllably increased in relation to the PBG structure relative to when the pump signal is incident on the PBG structure without the control signal. Such dramatic changes in the non-linear reflectivity and transmissivity occur over an advantageously small distance of only a few microns within the PBG structure. Efficient, compact, and easily controlled non-linear optical devices, such as a non-linear optical mirror, a non-linear optical amplifier, and a non-linear optical limiter can thus be realized using the techniques of the present invention.
According to one aspect of the present invention, a method of controlling the non-linear reflectivity of a first photonic signal incident on a PBG structure is provided. The method includes applying a second photonic signal to the PBG structure while the first photonic signal is incident on the PBG structure. The first and second signals interact with each other and with the PBG structure to increase the non-linear reflectivity of the first signal in relation to the PBG structure, relative to when only the first signal is applied to the PBG structure.
According to another aspect of the present invention, a method of controlling a non-linear transmissivity of a first photonic signal incident on a PBG structure is provided. The method includes applying a second photonic signal to the PBG structure while the first photonic signal is incident on the PBG structure. The first and second signals interact with each other and with the PBG structure to increase the non-linear transmissivity of the first signal in relation to the PBG structure, relative to when only the first signal is applied to the PBG structure.
According to yet another aspect of the present invention, a device for controlling the non-linear reflectivity of a first photonic signal incident on the device comprises a PBG structure including a plurality of material layers exhibiting a first order band gap edge and a second order band gap edge. The first order band gap edge is at a relatively low frequency near a frequency of the first photonic signal. The second order band gap is at a relatively high frequency greater than the low frequency of the first order band gap edge. The device further includes a second photonic signal for controlling the non-linear reflectivity of the first photonic signal. While the first photonic signal is incident on the PBG structure, the second photonic signal is applied to and removed from the PBG structure to thereby control the non-linear reflectivity thereof.
According to an even further aspect of the present invention, a device for controlling the non-linear transmissivity of a first photonic signal incident on the device comprises a PBG structure including a plurality of material layers exhibiting a low frequency, first order band gap edge near a frequency of the first photonic signal, and a high frequency, second order band gap edge. The device further includes a second photonic signal for controlling the non-linear transmissivity of the first photonic signal in response to applying the second photonic signal to and removing the second photonic signal from the PBG structure while the first photonic signal is incident on the PBG structure.
Further embodiments, features, and advantages of the present inventions, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.